Short communication: anomalous image quality phantom scores in magnification mammography: evidence of phase contrast enhancement.

Anomalously high image quality scores were noted for images of the Leeds TORMAM phantom obtained using magnification mammography. Comparison of optical density profiles of fibre features in the images with non-magnified images and images previously obtained using an in-line phase contrast geometry showed the presence of phase contrast enhancement in the magnification images. The effect on the phantom score is particularly marked for this design of phantom owing to its use of fibres, which tend to enhance well. A large proportion of the phantom score is associated with fibrous features. It is concluded that direct comparison of TORMAM phantom scores from magnified images with those from non-magnified images is not valid due to the different balance of physical mechanisms forming the two kinds of image.